a) Field of the Invention
The present invention relates to a rubber-made sealing closure (which may also be called a “rubber cap” or “rubber closure”) adapted to be fitted on a liquid-medicine-injecting port (Luer nozzle) of a syringe/container with a medicament contained therein so that a solid or liquid injectable preparation contained as the medicament in the syringe/container can be sealed in place to maintain its quality over an extended period of time. The sealing closure has a plastic film laminated thereon at least at an area of an inner wall thereof, where the sealing closure is to be brought into or maintained in contact with the solid or liquid injectable preparation.
b) Description of the Related Art
For medicament containers, especially containers for injectable preparations, strict sealing performance is specified and required as their function in the Pharmacopoeia, to say nothing of the quality of the container material. Accordingly, rubber-made sealing closures in the form of single pieces of rubber without any plastic film laminated thereon have been used because they are considered to be the best in sealing performance.
On the other hand, rubber-made caps which are used with syringes as medical devices are different from sealing rubber closures employed with general containers for injectable preparations such as vials in that the sealing rubber closures normally remain in contact with liquid medicines (the Pharmacopoeia specifies certain quality standards required for the sealing rubber closures).
It is indicated that, when new drugs of these days are brought into direct contact with a rubber material, their active ingredients undergo modifications, thereby making it difficult to maintain their stability over an extended period of time.
Sealing rubber closures for syringe/containers with medicaments filled and sealed therein in advance (which will hereinafter be called “prefilled syringes” on the authority of ISO 11040-1 and the like) are mostly made of a rubber material alone.
An injectable liquid preparation, which has been formulated in a form filled and sealed in a prefilled syringe, always remains in contact with a sealing rubber closure as opposed to an active ingredient in a medicinal preparation contained in a vial (a vessel of small capacity), so that the active ingredient in the injectable liquid preparation in the prefilled syringe tends to receive greater chemical influence from the rubber closure. From the standpoint of protection of the active ingredient from contamination, the conditions under which the active ingredient is placed are severe.
Concerning prefilled syringes themselves, a variety of proposals have been made to date for example, in JP kokai 7-313598 (syringe-shaped container), JP kokai 8-280800 (prefilled syringe for two-part injectable preparation), JP kokai 8-317975 (prefilled syringe and a stopper assembly therefor), and EP 07 09 105A (prefilled syringe and production process of the same). These publications all disclose the structures and function of prefilled syringes, but make no mention whatsoever about the quality and function of sealing rubber closures employed for the sealing of the prefilled syringes.
In connection with rubber closures, on the other hand, the present assignee disclosed in JP kokai 62-139668 (laminated plug for syringe) various examples of rubber-made sliding plugs (plungers) for prefilled syringes, said plugs being laminated at surfaces thereof with tetrafluoroethylene-ethylene copolymer films, and one example of a rubber plug for a front end portion of a syringe (see FIG. 9 in the kokai publication; FIG. 2A in this application). The rubber plug for the front end portion of the syringe, which is disclosed by way of example in the kokai publication, is indicated to be kept out of contact with a liquid medicine owing to the laminated film. Its Luer-nozzle-receiving part (a part in which a liquid-medicine-injecting port is inserted) is however configured in a substantially cylindrical, tapered form (i.e., the diameter on a side of an inner end portion is smaller than the diameter on a side of a Luer-nozzle-receiving opening). Accordingly, the Luer nozzle tends to fall out and sealing performance is hardly available, although the Luer-nozzle-receiving part is formed with an average outer diameter smaller than that of the associated Luer nozzle.
With a view-to overcoming this problem, the present inventors attempted to close a free end aperture of the Luer nozzle by forming the Luer-nozzle-receiving part of the rubber closure into an untapered cylindrical form (the diameter of which was smaller than the maximum diameter of the Luer nozzle) as shown in FIG. 2B and then forming a small bead on an inner end wall of the Luer-nozzle-receiving part as depicted in FIG. 2C. However, the insertion of the Luer nozzle was not smoothly performed and, when the Luer nozzle was inserted, wrinkles were developed in the laminated film, thereby failing to obtain satisfactory sealing performance.
As has been described above, the conventionally proposed sealing rubber closures in which the front ends of syringes are to be inserted have fluorinated resin films laminated on inner walls thereof, so that the rubber closures are maintained out of direct contact with their corresponding liquid medicines. Since a fluorinated resin has high stiffness and can be hardly deformed, it must inherently apply high fastening force to the Luer nozzle inserted in the rubber closure. However, the inner wall of the rubber closure is formed in a substantially cylindrical form which has substantially the same taper as the Luer nozzle, and the fluorinated resin has small frictional resistance with other materials. Especially in the case of a plastic-made syringe, the inserted Luer nozzle therefore tends to slide. Compared with a rubber closure not laminated with a fluorinated resin film, the rubber closure with the fluorinated resin film laminated thereon is inferior in sealing performance. Therefore, the rubber closure with the fluorinated resin film laminated thereon is not suited for practical use and requires improvements in sealing performance. If the Luer-nozzle-receiving part of the rubber closure is configured in an untapered cylindrical form, on the other hand, the Luer nozzle cannot be inserted smoothly, and wrinkles are hence formed in the laminated film, thereby failing to obtain satisfactory sealing performance.